I would like to apologize everyone who was trying to use Wikidot for the last few hours, but could not log-in or could not edit pages, without getting any reasonable error message from Wikidot. It took us more than a crazy hour to nail the problem and fix it.
The problem was caused by a piece of profiling code that was added to Wikidot by one of our developers. The code was added outside of our usual workflow, not even through the our version control system (git), thus skipping the internal review process. Moreover, the code was causing an error in a few places, but was silently damping all error messages, and not leaving any trace in the logs. This fooled us and we were rather suspecting lower-level problems with our main server.
Thankfully we got a bunch of emails with reports that something is wrong with Wikidot (thanks!), so we could start working on it quickly.
This was a clear mistake on our side and I am sorry for the problems it have caused. I believe we will make our internal process stricter, and avoid such problems in the future.